There is now strong evidence that neuronal interactions in vesicourethral ganglia play a key role in autonomic neural control of the bladder and uretha. The structural basis of these interactions has remained largely speculative because of the lack of morphologic information on neurosynaptic organization of the ganglia. This study will provide this information by a multimodal morphologic approach that has not been applied previously for this purpose. The neurohistochemistry and ultrastructure of vesicourethral (and functionally related) ganglia from male cats subjected to specially designed surgical neuroectomies, with or without chemical sympathectomy, will be analyzed qualitatively and quantitatively in comparison to ganglia from normal animals. This analysis will provide new information on: (1) the relative abundance of adrenergic, cholinergic and small intensely fluorescent (SIF) neurons; (2) the source of preganglionic synapses of each neuron type; (3) the presence, distribution and origin of postganglionic synapses established by adrenergic (postganglionic sympathetic) and postganglionic cholinergic (parasympathetic) neural elements; (4) the contribution of SIF and non-SIF interneurons to intraganglionic synapses; and (5) the morphologic types of synapses, and the structural identity of their presynaptic and postsynaptic components. The data to be obtained will be correlated with available physiopharmacologic observations to develop a working neurosynaptic model of vesicourethral ganlia. This model will fill important gaps in our knowledge of the role of infraspinal neuronal interaction mechanisms in micturition, and thereby provide a solid basis for: (1) the understanding of neural mechanisms of normal micturition in man; (2) the planning of future investigation of anatomical and functional deficits in neurogenic vesical dysfunction, in experimental animals and in man; and (3) the precise definition of mechanisms of autonomic drug actions on the vesicourethral muscularis, and the rationale for their clinical use in the diagnosis and treatment of various disorders of micturition.